Isobars of elements have same :

Isobars are defined as atoms of different chemical elements that possess the same mass number (A) but different atomic numbers (Z) [1]. The mass number represents the total count of nucleons, which is the sum of protons and neutrons within the atomic nucleus. While isotopes of a single element share the same atomic number but differ in mass, isobars belong to different elements and thus have distinct chemical properties and different numbers of protons and electrons [1]. For example, the series 40S, 40Cl, 40Ar, 40K, and 40Ca all share a mass number of 40, making them isobars despite having different numbers of protons and neutrons [1]. Therefore, the defining characteristic that isobars have in common is their mass number, which determines the total weight of the nucleus [2].

Sources

1. [2] https://www.khanacademy.org/science/biology/history-of-life-on-earth/radiometric-dating/a/atomic-number-atomic-mass-and-isotopes-article